Hmm interesting. Lost sky news.
C48 comes in ok but c52 is the same signal strength but poor quality.
Receiving from sandy heath in south stevenage.
I used to live in the old town years ago!
But you should be OK according to this: http://www.ukfree.tv/txdetail.php?a=TL204494
Are you by any chance using an old Group A aerial? - you should be using a wideband. & are there any close trees etc in the northern direction from you? they can have odd effects sometimes, blocking certain frequencies for example.
No. Based near the football ground so I am in a slight dip in the land. As for the aerial, A megaboost log aerial with a £60 distrobution amp. My only gripe is that the aerial height is not as high as i wanted as screw fix did not have any 3 meter poles in stock.
Looks like i will have to put up with it for now.
Good news though is that film 4 and yesterday channels are working fine, which is a bonus.
OK, Cambs & Beds = signals from Sandy heath
East anglia = Tacolneston, though I would be surprised even with last nights power increase that you were getting Tac, are you on the East side of Cambridge or on high ground?
I'm a couple of miles directly South of Cambridge. I guess we do have what pass for hills on this side of Cambridge!
OK, Cambs & Beds = signals from Sandy heath
East anglia = Tacolneston and Sudbury.
There - fixed that for you...;)
And no, to whoever asked, it appears that 63 on Sudbury is going to remain poor until next year (remember, Sandy is kicking out ArqB @ 170,000 watts, Tac is doing ArqB @ 100,000 watts and Sudbury is showing the same mux at 2,200 watts - coverage is going to be poor until Kent/London switch over, in the meantime you might try and see if you can get the more powerful versions instead, although I realise that isn't practical for a lot of people)
Did anyone spot the mistake in Arqiva's Press Release,
saying that the Tacolneston Transmitter was switched off on the 23rd of September instead of November?
Fortunately the reception from the new Lowestoft relay (wrong polarity and about 110 off bearing) is too poor to be automatically stored by any of the other sets in the house.
In Clacton my tv has other channels from 750 through to 999, mainly belmont aand sandy heath frequencies that were stored during the lift conditions of the past week.
I have noticed that my tv totally ignores the Clacton Relay during a scan(even though I can see it from the end of my road), I assume this is because it is a carbon copy of what Sudbury is transmitting and it automaticly choses Sudbury because it is the strongest signal out of the 2.
I'm a couple of miles directly South of Cambridge. I guess we do have what pass for hills on this side of Cambridge!
Is that the Gogs? I remember getting involved with some Pirate broadcasting there years ago.....but that's another story....:cool:
The map here http://www.ukfree.tv/txdetail.php?a=TM131958 does show Tac just about makes it there - & that is the older map, Tac now uses a higher one, with the Digital on top.
And no, to whoever asked, it appears that 63 on Sudbury is going to remain poor until next year (remember, Sandy is kicking out ArqB @ 170,000 watts, Tac is doing ArqB @ 100,000 watts and Sudbury is showing the same mux at 2,200 watts - coverage is going to be poor until Kent/London switch over, in the meantime you might try and see if you can get the more powerful versions instead, although I realise that isn't practical for a lot of people)
So Sudbury gives the same transmitter info as Tacolneston? that is REALLY clever of Aquiva:)
Thankfully, Sudbury does not make it to Thetford forest, though their maps say it does - perhaps Bury Sugar factory gets in the way?:) http://www.ukfree.tv/txdetail.php?a=TL913377
Has anyone in North Norfolk, who were not getting Tac before, finding an improvement with the signal now?
So is there any more news with what's going on with ArqB on ch63 at Sudbury?
Basically, we get what we have until next June. I've been in correspondence with Digital UK, trying to make a case both with theoretical arguments (e.g. free-space path loss is increased by 1.2dB between ch50 & ch63), and real measurements (ch63 around 10dB lower with me than was ch50), but the upshot is that there will be no change. To be fair, they did refer my correspondence to their techies, but they can't up the power. To quote: "the transmission power for this group of channels was doubled to from 1.1kW to 2.2kW at the second stage of switchover on 20 July 2011, this used all the available transmitter power headroom and there is no more transmitter power available on this channel". This implies a technical limitation, but could posssibly mean an administrative limit, as 2.2kW would have been agreed with OFCOM.
I won't go any further with this. I suppose if they get a deluge of complaints from SE Essex & E Suffolk, they might try to investigate a bit further, but I'm not holding my breath.
Basically, we get what we have until next June. I've been in correspondence with Digital UK, trying to make a case both with theoretical arguments (e.g. free-space path loss is increased by 1.2dB between ch50 & ch63), and real measurements (ch63 around 10dB lower with me than was ch50), but the upshot is that there will be no change. To be fair, they did refer my correspondence to their techies, but they can't up the power. To quote: "the transmission power for this group of channels was doubled to from 1.1kW to 2.2kW at the second stage of switchover on 20 July 2011, this used all the available transmitter power headroom and there is no more transmitter power available on this channel". This implies a technical limitation, but could posssibly mean an administrative limit, as 2.2kW would have been agreed with OFCOM.
I won't go any further with this. I suppose if they get a deluge of complaints from SE Essex & E Suffolk, they might try to investigate a bit further, but I'm not holding my breath.
I'm not convinced that ArqB on Sudbury CH63 is delivering the field strengths that DigitalUK think it is. Three reasons.
1. The 8.8 dB discrepancy between Jcsager's real measurements and the theoretical 1.2 dB.
2. Before I changed my aerial last June I was using a 1977 J-Beam (MBM48?) Group B aerial and could get all the muxes including the weak one on "Sudbury B" (Ch54 or 56 - I can't remember). (Not the higher power version in the 60s with an aerial null to the east.) Was that on 1.1kW? Now with a 52 element wideband aerial which is 2 feet higher, my reception of C63 is right on the edge. My Echostar manages to give clear pictures and sound for seconds at a time whereas another three STBs usually don't acknowledge that ArqB exists.
3. The digitaluk post code predictor says that my current reception of ArqB should be better than both ArqA and MuxA/SDN. But it is much worse.
No, they're coming in considerably weaker than the Sandy Heath HD Mux, BBC A and D3/4 on UHF 21, 24 and 27. But Arq A and Arq B from Sandy Heath are considerably stronger than the old 20KW pre DSO muxes including the current Mux A on UHF 31. I'd say Arq A and Arq B are pretty much mid way in signal strength between Mux A (20KW) and the PSB muxes (unknown power since there is a pending "PSB power up" event at Sandy Heath in 2012).
Some time back on this forum someone with better equipment reckoned Arq B Sandy Heath was being broadcast at 60KW, and that was consistent with the dbm relative measurements of my Nokia 221T when I took them carefully enough. Arq B is still at that signal strength on my box and Arq A is about the same, so best guess seems to be both are on something interim around 60KW.
I just did the retune for Sandy Heath on my Humax. All went well, but right at the end it wanted me to select either:
East Anglia
or
Cambridgeshire&Bedfordshire
whats the difference? East Anglia was highlighted as default but I actually chose Cambs&Beds seeing as I am in Cambridge. Is this correct?
If you're using an HDR Fox T2 it doesn't make any difference which you select because the box ignores what you say and tunes into all muxes. It uses the higher UHF channel number ones as the main channels and bumps any earlier ones into the 800s. At this point Accurate Recording doesn't work, it gives an "Unable to track" result.
I suggest you tune manually, entering just the UHF channel numbers for your transmitter. You'll need to start an automatic tune and then cancel it and save stored channels (which should be none), this is the only way to delete all existing channels. Then tune in your 6 muxes one by one, remembering to select DVB-T2 for HD mux and DVB-T for the other 5.
Sky Text used to be much better. Like the rest of Sky's channels on Freeview, it has been on a slippery slope since it launched.
Yes, I used to watch Sky 3 on Freeview. The first season of Tru Calling was quite good, then they just started repeating it and then showing season 2 episodes in a strange order in the middle of the night. I also got into Battlestar Galactica due to watching season 1 on Sky 3, but then they never showed any of the other seasons and I borrowed DVD boxsets from friends to watch the rest of it.
I sometimes wonder why Sky briefly made an effort on Freeview and then the channels deteriorated. The cynic in me suggests this was a ploy to get people to like Sky channels, then reduce the quality on Freeview to try to get people to take out a Sky subscription. All it did in my case is make me hate the evil empire of $ky and Murdoch even more.
So Sudbury gives the same transmitter info as Tacolneston? that is REALLY clever of Aquiva
The decision to do this is not down to Arqiva alone.
It is due to the UK's DTT technical architecture and that both transmitter sites are fed with the same Service Insertion Point, Service/Schedule Information (SIPSI). There are around 29 different ones throughout the UK - reflecting the different 'regions and nations' of the BBC and commercial broadcasters.
SIPSI equipment is 'shared' by all the broadcasters and itself is fed epg data from a 'central collator' - originally run by OnDigital, now Freeview.
In the particular case of Sudbury, it will be considered a 'daughter' of Tacolneston in the same way as it was a 'relay' of it in the analogue days (albeit fed baseband over a SHF link).
No it isn't, the best guess is around 60,000 watts but definitely not as strong as PSB muxes. See my other posting for more detail.
Apologies - I was working off the final situation which is 170KW.
The only COM PowerUp mentioned on DigitalUK seems to relate to SDN on 9th May.
There is a PSB PowerUp but the numbers only change for BBC and D3&4, and not by much.
There are a couple of Reception Changes, but these are more likely to be due to increase/decrease in interference from other transmitters during work on Meridian/London DSO.
Apologies - I was working off the final situation which is 170KW.
The only COM PowerUp mentioned on DigitalUK seems to relate to SDN on 9th May.
There is a PSB PowerUp but the numbers only change for BBC and D3&4, and not by much.
There are a couple of Reception Changes, but these are more likely to be due to increase/decrease in interference from other transmitters during work on Meridian/London DSO.
Yes I am aware of this, there is no advertised future power up for Arq A or Arq B from Sandy Heath. Nevertheless, both my measurements and other posters show that they are significantly under powered (around a third of what they should be) compared to the PSB muxes at the moment (and the PSB muxes aren't on full power yet either).
Does anyone else have a broken white line long the very top of the picture on ITV1? Im receiving Cambs & Beds. Its been there for a while, very distracting, have to watch East Midlands ITV1 instead. It was like it on CH5 a while back.
No, they're coming in considerably weaker than the Sandy Heath HD Mux, BBC A and D3/4 on UHF 21, 24 and 27. But Arq A and Arq B from Sandy Heath are considerably stronger than the old 20KW pre DSO muxes including the current Mux A on UHF 31. I'd say Arq A and Arq B are pretty much mid way in signal strength between Mux A (20KW) and the PSB muxes (unknown power since there is a pending "PSB power up" event at Sandy Heath in 2012).
Some time back on this forum someone with better equipment reckoned Arq B Sandy Heath was being broadcast at 60KW, and that was consistent with the dbm relative measurements of my Nokia 221T when I took them carefully enough. Arq B is still at that signal strength on my box and Arq A is about the same, so best guess seems to be both are on something interim around 60KW.
Thanks for that, I would also think the electricity consumption at stations such as Sandy heath has just dropped like a stone - with 4 old analogue transmitters - each belting out 1000kw of RF power (not sure of the efficiency though?) + the lower power Digital stuff - nearly all being turned off & replaced by much lower digital power - Their next electricity bill should be a pleasure to read, in comparison anyway:) - multiply this over all the main analogue transmitting stations that are being, or have been shut down, this should result in a considerable saving.
Thanks for that, I would also think the electricity consumption at stations such as Sandy heath has just dropped like a stone - with 4 old analogue transmitters - each belting out 1000kw of RF power (not sure of the efficiency though?) + the lower power Digital stuff - nearly all being turned off & replaced by much lower digital power - Their next electricity bill should be a pleasure to read, in comparison anyway:) - multiply this over all the main analogue transmitting stations that are being, or have been shut down, this should result in a considerable saving.
The old analogue transmissions were 1000KW ERP ie. Effective Radiated Power and the pre-DSO digital were 20KW ERP. This includes a considerable amount of antenna gain, just the same as your wideband or group A or whatever yagi or X beam on the roof has gain. So the 1000KW isn't a direct measure of electricity consumption. On the other hand it does all scale, so the electricity bill will go down quite a bit.
You also have to factor in the efficiency of the RF amplifiers, I don't know what efficiency Klystrons had. One of the reasons for using MSDT IOTs (google it, they're a type of valve) for the 3 PSB muxes plus SDN is they are about 45% efficient ie. 55% of the electricty they consume produces heat and the other 45% goes into the RF output. Arq A and Arq B are using solid state transmitters which are only about 20% efficient so will consume twice the electricity for a given RF output power compared to the IOTs. Quite why Arq A and Arq B at the main stations aren't using IOTs is unclear.
Then there are combiner and feeder losses ie. how much power you lose combining all the signals together and feeding them up the massive coaxs that go up the mast. Any losses here again produce heat.
Relays and smaller main sites don't use IOTs, below a certain power output it's simply easier to use solid state RF amplifiers. The IOTs need multi kilovolt high voltage generators and need forced cooling, usually with an oil cooling system. Below a certain power output it isn't worth the faff of using them.
The old analogue transmissions were 1000KW ERP ie. Effective Radiated Power and the pre-DSO digital were 20KW ERP. This includes a considerable amount of antenna gain, just the same as your wideband or group A or whatever yagi or X beam on the roof has gain. So the 1000KW isn't a direct measure of electricity consumption. On the other hand it does all scale, so the electricity bill will go down quite a bit.
You also have to factor in the efficiency of the RF amplifiers, I don't know what efficiency Klystrons had. One of the reasons for using MSDT IOTs (google it, they're a type of valve) for the 3 PSB muxes plus SDN is they are about 45% efficient ie. 55% of the electricty they consume produces heat and the other 45% goes into the RF output. Arq A and Arq B are using solid state transmitters which are only about 20% efficient so will consume twice the electricity for a given RF output power compared to the IOTs. Quite why Arq A and Arq B at the main stations aren't using IOTs is unclear.
Then there are combiner and feeder losses ie. how much power you lose combining all the signals together and feeding them up the massive coaxs that go up the mast. Any losses here again produce heat.
Relays and smaller main sites don't use IOTs, below a certain power output it's simply easier to use solid state RF amplifiers. The IOTs need multi kilovolt high voltage generators and need forced cooling, usually with an oil cooling system. Below a certain power output it isn't worth the faff of using them.
Thanks for the info Owen - understood some of it! But my only experience of Big RF equipment in the flesh (so to speak), were the Continental & RCA 50KW MW Transmitters used on the Mi Amigo & the Ross Revenge (Radio Caroline) - I know they used some pretty hefty voltage on their output valves
I did find this http://www.axcera.com/downloads/technotes-whitepapers/technote_6.pdf via google, definetly a Mastermind specilist subject:D
Perhaps Aqu A & B are using the more inefficient TXs, because they are a bit cheaper to buy?
Rob
Thanks for the info Owen - understood some of it! But my only experience of Big RF equipment in the flesh (so to speak), were the Continental & RCA 50KW MW Transmitters used on the Mi Amigo & the Ross Revenge (Radio Caroline) - I know they used some pretty hefty voltage on their output valves
I did find this http://www.axcera.com/downloads/technotes-whitepapers/technote_6.pdf via google, definetly a Mastermind specilist subject:D
Perhaps Aqu A & B are using the more inefficient TXs, because they are a bit cheaper to buy?
Rob
At low frequencies (I think MW counts), the output power quoted is the power of the RF amplifier (or at least it was many years ago, I'm not sure of current practice). This is because the aerial has loss not gain in it, since you can't sensibly construct a big enough monster antenna to have gain at long wavelengths. This has the disadvantage that the quoted power of the transmitter gives you no real clue as to the chances of receiving it. I suspect historically the world started this way, then switched to ERP when they got up to frequencies where we could actually get some gain from the antenna so the signal was stronger than the amp implied. It's probably all about "my output power's bigger than yours" so no-one is truthful about long wavelength effective radiated power.
At low frequencies (I think MW counts), the output power quoted is the power of the RF amplifier (or at least it was many years ago, I'm not sure of current practice). This is because the aerial has loss not gain in it, since you can't sensibly construct a big enough monster antenna to have gain at long wavelengths. This has the disadvantage that the quoted power of the transmitter gives you no real clue as to the chances of receiving it. I suspect historically the world started this way, then switched to ERP when they got up to frequencies where we could actually get some gain from the antenna so the signal was stronger than the amp implied. It's probably all about "my output power's bigger than yours" so no-one is truthful about long wavelength effective radiated power.
Yes, MW aerials are not very efficent beasts! Though I think the ships both did very well signal wise, because the sea itself seemed to do a lot of the radiating of the signal! - being a perfect earth I guess helped a lot.
Comments
I used to live in the old town years ago!
But you should be OK according to this:
http://www.ukfree.tv/txdetail.php?a=TL204494
Are you by any chance using an old Group A aerial? - you should be using a wideband. & are there any close trees etc in the northern direction from you? they can have odd effects sometimes, blocking certain frequencies for example.
Looks like i will have to put up with it for now.
Good news though is that film 4 and yesterday channels are working fine, which is a bonus.
I'm a couple of miles directly South of Cambridge. I guess we do have what pass for hills on this side of Cambridge!
And no, to whoever asked, it appears that 63 on Sudbury is going to remain poor until next year (remember, Sandy is kicking out ArqB @ 170,000 watts, Tac is doing ArqB @ 100,000 watts and Sudbury is showing the same mux at 2,200 watts - coverage is going to be poor until Kent/London switch over, in the meantime you might try and see if you can get the more powerful versions instead, although I realise that isn't practical for a lot of people)
Ah, they've corrected it then. That was still wrong a couple of weeks ago.
@OwenSmith
Sky Text used to be much better. Like the rest of Sky's channels on Freeview, it has been on a slippery slope since it launched.
saying that the Tacolneston Transmitter was switched off on the 23rd of September instead of November?
You can read it here
http://www.arqiva.com/corporate/press/archive/2011/2011-11-23%20-%20Tacolneston%20switchover%20completes%20Anglia%20region.pdf
In Clacton my tv has other channels from 750 through to 999, mainly belmont aand sandy heath frequencies that were stored during the lift conditions of the past week.
I have noticed that my tv totally ignores the Clacton Relay during a scan(even though I can see it from the end of my road), I assume this is because it is a carbon copy of what Sudbury is transmitting and it automaticly choses Sudbury because it is the strongest signal out of the 2.
Is that the Gogs? I remember getting involved with some Pirate broadcasting there years ago.....but that's another story....:cool:
The map here http://www.ukfree.tv/txdetail.php?a=TM131958 does show Tac just about makes it there - & that is the older map, Tac now uses a higher one, with the Digital on top.
So Sudbury gives the same transmitter info as Tacolneston? that is REALLY clever of Aquiva:)
Thankfully, Sudbury does not make it to Thetford forest, though their maps say it does - perhaps Bury Sugar factory gets in the way?:)
http://www.ukfree.tv/txdetail.php?a=TL913377
Has anyone in North Norfolk, who were not getting Tac before, finding an improvement with the signal now?
Basically, we get what we have until next June. I've been in correspondence with Digital UK, trying to make a case both with theoretical arguments (e.g. free-space path loss is increased by 1.2dB between ch50 & ch63), and real measurements (ch63 around 10dB lower with me than was ch50), but the upshot is that there will be no change. To be fair, they did refer my correspondence to their techies, but they can't up the power. To quote: "the transmission power for this group of channels was doubled to from 1.1kW to 2.2kW at the second stage of switchover on 20 July 2011, this used all the available transmitter power headroom and there is no more transmitter power available on this channel". This implies a technical limitation, but could posssibly mean an administrative limit, as 2.2kW would have been agreed with OFCOM.
I won't go any further with this. I suppose if they get a deluge of complaints from SE Essex & E Suffolk, they might try to investigate a bit further, but I'm not holding my breath.
Last night only 60 services available and now today back up to 89 but none of the above channels.
I know I really need a proper aerial but as I've got SKY it's not a priority, just enquiring as to why the 'above' happens?
Thanks.
I'm not convinced that ArqB on Sudbury CH63 is delivering the field strengths that DigitalUK think it is. Three reasons.
1. The 8.8 dB discrepancy between Jcsager's real measurements and the theoretical 1.2 dB.
2. Before I changed my aerial last June I was using a 1977 J-Beam (MBM48?) Group B aerial and could get all the muxes including the weak one on "Sudbury B" (Ch54 or 56 - I can't remember). (Not the higher power version in the 60s with an aerial null to the east.) Was that on 1.1kW? Now with a 52 element wideband aerial which is 2 feet higher, my reception of C63 is right on the edge. My Echostar manages to give clear pictures and sound for seconds at a time whereas another three STBs usually don't acknowledge that ArqB exists.
3. The digitaluk post code predictor says that my current reception of ArqB should be better than both ArqA and MuxA/SDN. But it is much worse.
No, they're coming in considerably weaker than the Sandy Heath HD Mux, BBC A and D3/4 on UHF 21, 24 and 27. But Arq A and Arq B from Sandy Heath are considerably stronger than the old 20KW pre DSO muxes including the current Mux A on UHF 31. I'd say Arq A and Arq B are pretty much mid way in signal strength between Mux A (20KW) and the PSB muxes (unknown power since there is a pending "PSB power up" event at Sandy Heath in 2012).
Some time back on this forum someone with better equipment reckoned Arq B Sandy Heath was being broadcast at 60KW, and that was consistent with the dbm relative measurements of my Nokia 221T when I took them carefully enough. Arq B is still at that signal strength on my box and Arq A is about the same, so best guess seems to be both are on something interim around 60KW.
If you're using an HDR Fox T2 it doesn't make any difference which you select because the box ignores what you say and tunes into all muxes. It uses the higher UHF channel number ones as the main channels and bumps any earlier ones into the 800s. At this point Accurate Recording doesn't work, it gives an "Unable to track" result.
I suggest you tune manually, entering just the UHF channel numbers for your transmitter. You'll need to start an automatic tune and then cancel it and save stored channels (which should be none), this is the only way to delete all existing channels. Then tune in your 6 muxes one by one, remembering to select DVB-T2 for HD mux and DVB-T for the other 5.
No it isn't, the best guess is around 60,000 watts but definitely not as strong as PSB muxes. See my other posting for more detail.
Yes, I used to watch Sky 3 on Freeview. The first season of Tru Calling was quite good, then they just started repeating it and then showing season 2 episodes in a strange order in the middle of the night. I also got into Battlestar Galactica due to watching season 1 on Sky 3, but then they never showed any of the other seasons and I borrowed DVD boxsets from friends to watch the rest of it.
I sometimes wonder why Sky briefly made an effort on Freeview and then the channels deteriorated. The cynic in me suggests this was a ploy to get people to like Sky channels, then reduce the quality on Freeview to try to get people to take out a Sky subscription. All it did in my case is make me hate the evil empire of $ky and Murdoch even more.
It is due to the UK's DTT technical architecture and that both transmitter sites are fed with the same Service Insertion Point, Service/Schedule Information (SIPSI). There are around 29 different ones throughout the UK - reflecting the different 'regions and nations' of the BBC and commercial broadcasters.
SIPSI equipment is 'shared' by all the broadcasters and itself is fed epg data from a 'central collator' - originally run by OnDigital, now Freeview.
In the particular case of Sudbury, it will be considered a 'daughter' of Tacolneston in the same way as it was a 'relay' of it in the analogue days (albeit fed baseband over a SHF link).
The only COM PowerUp mentioned on DigitalUK seems to relate to SDN on 9th May.
There is a PSB PowerUp but the numbers only change for BBC and D3&4, and not by much.
There are a couple of Reception Changes, but these are more likely to be due to increase/decrease in interference from other transmitters during work on Meridian/London DSO.
Yes I am aware of this, there is no advertised future power up for Arq A or Arq B from Sandy Heath. Nevertheless, both my measurements and other posters show that they are significantly under powered (around a third of what they should be) compared to the PSB muxes at the moment (and the PSB muxes aren't on full power yet either).
Thanks for that, I would also think the electricity consumption at stations such as Sandy heath has just dropped like a stone - with 4 old analogue transmitters - each belting out 1000kw of RF power (not sure of the efficiency though?) + the lower power Digital stuff - nearly all being turned off & replaced by much lower digital power - Their next electricity bill should be a pleasure to read, in comparison anyway:) - multiply this over all the main analogue transmitting stations that are being, or have been shut down, this should result in a considerable saving.
The old analogue transmissions were 1000KW ERP ie. Effective Radiated Power and the pre-DSO digital were 20KW ERP. This includes a considerable amount of antenna gain, just the same as your wideband or group A or whatever yagi or X beam on the roof has gain. So the 1000KW isn't a direct measure of electricity consumption. On the other hand it does all scale, so the electricity bill will go down quite a bit.
You also have to factor in the efficiency of the RF amplifiers, I don't know what efficiency Klystrons had. One of the reasons for using MSDT IOTs (google it, they're a type of valve) for the 3 PSB muxes plus SDN is they are about 45% efficient ie. 55% of the electricty they consume produces heat and the other 45% goes into the RF output. Arq A and Arq B are using solid state transmitters which are only about 20% efficient so will consume twice the electricity for a given RF output power compared to the IOTs. Quite why Arq A and Arq B at the main stations aren't using IOTs is unclear.
Then there are combiner and feeder losses ie. how much power you lose combining all the signals together and feeding them up the massive coaxs that go up the mast. Any losses here again produce heat.
Relays and smaller main sites don't use IOTs, below a certain power output it's simply easier to use solid state RF amplifiers. The IOTs need multi kilovolt high voltage generators and need forced cooling, usually with an oil cooling system. Below a certain power output it isn't worth the faff of using them.
Thanks for the info Owen - understood some of it! But my only experience of Big RF equipment in the flesh (so to speak), were the Continental & RCA 50KW MW Transmitters used on the Mi Amigo & the Ross Revenge (Radio Caroline) - I know they used some pretty hefty voltage on their output valves
I did find this http://www.axcera.com/downloads/technotes-whitepapers/technote_6.pdf via google, definetly a Mastermind specilist subject:D
Perhaps Aqu A & B are using the more inefficient TXs, because they are a bit cheaper to buy?
Rob
At low frequencies (I think MW counts), the output power quoted is the power of the RF amplifier (or at least it was many years ago, I'm not sure of current practice). This is because the aerial has loss not gain in it, since you can't sensibly construct a big enough monster antenna to have gain at long wavelengths. This has the disadvantage that the quoted power of the transmitter gives you no real clue as to the chances of receiving it. I suspect historically the world started this way, then switched to ERP when they got up to frequencies where we could actually get some gain from the antenna so the signal was stronger than the amp implied. It's probably all about "my output power's bigger than yours" so no-one is truthful about long wavelength effective radiated power.
Yes, MW aerials are not very efficent beasts! Though I think the ships both did very well signal wise, because the sea itself seemed to do a lot of the radiating of the signal! - being a perfect earth I guess helped a lot.